Cardiovascular risk factors among Ecuadorian adolescents : a school-based health promotion intervention

Non-communicable diseases (NCDs) are the leading cause of death worldwide. More than 80% of deaths from cardiovascular diseases (CVD) and diabetes occur in low- and middle-income countries (LMICs). Identifying and understanding the distribution of risk factors is key to developing effective population intervention programs to prevent NCDs. These preventive strategies should start in youth. In Ecuador diabetes mellitus, hypertension, stroke, ischemic heart disease and heart failure rank high on a list of the ten leading causes of death in the general population. Furthermore, overweight and obesity are prevalent risk factors among adolescents. This thesis aims to: (i) explore the distribution of CVD risk factors with a major focus on diet among adolescents living in urban and rural settings from different socio-economic backgrounds, (ii) analyze the effect on dietary intake, body mass index (BMI), waist circumference and blood pressure of a school-based health promotion intervention, (iii) describe the process evaluation (PE) of the school-based health promotion intervention and, (iv) link the PE data with the intervention effect. To accomplish these objectives, two main activities were performed. A cross-sectional survey among 779 adolescents 10-16 years old from an urban and rural area in Ecuador was performed. The research aimed to identify the prevalence of metabolic CVD risk factors and the dietary intake of the target group. Dyslipidemia, abdominal obesity, high blood cholesterol and overweight were the most prevalent risk factors. The diet of this group of adolescents was carbohydrate based, rich in refined cereals, added sugar and processed foods consumed mainly in snacks. Consumption of fruit, vegetables, fish and oilseeds were very low. An estimated 18% of the adolescents reported skipping breakfast. Differences in dietary intake between urban and rural adolescents were small. Diets high in refined carbohydrates were associated with higher plasma glucose levels, while diets with high fat and low fiber content were correlated with increased levels of low density lipoprotein (LDL) and total blood cholesterol concentrations. The cross-sectional data was combined with theoretical approaches to design a culturally appropriate evidence and theory-based health promotion intervention. A pair matched cluster randomized controlled trial was implemented among 1430 adolescents attending 20 schools in Cuenca-Ecuador during 28 months from 2009-2012, 10 schools were allocated to the intervention group and the remaining ten to the control group. The program aimed to improve dietary intake, physical activity, sedentary behavior and physical fitness (primary outcomes) and reduce BMI, waist circumference and blood pressure (secondary outcomes). The intervention strategies combined the implementation of an individual classroom-based component with an environment-based component along the ten intervention schools. The individual-based component involved the implementation of an educational tool-kit, whilst, the environment-based component consisted in the delivery of educational workshops for parents and food-tuck shop staff. The normal standard curriculum was followed in the control schools. A detailed PE was also conducted. At the end of the intervention, data from 1079 adolescents from the 20 schools originally contacted was available for analysis. The program effectively increased fruit and vegetable intake and decreased added sugar and processed food intake during snacks. The intervention was also effective in decreasing waist circumference and blood pressure in favor of the intervention group. The effect on dietary intake was not moderated by the socioeconomic status or the weight or the age of the participants. However, the effect on waist circumference was higher among younger and overweight-obese adolescents. The program was correctly implemented and well received by the target audiences i.e. adolescents, teachers, parents and food-tuck shop staff. Dose, reach and fidelity were high with the exception of parental reach (only 15%). Barriers for program implementation were the difficulty to attach the program to the school curriculum, the low parental reach and, the resistance to a decrease in portion size served in the food-tuck shops. Although still below the nutritional recommendations, the combined effect of the intervention on several individual risk factors is encouraging and promising. It suggests that school-based interventions can address various risk factors simultaneously in adolescents from LMICs. This thesis provides new evidence for the prevention of NCDs among adolescents from LMICs